Fibroblast growth factor 21 variants

ABSTRACT

This present invention relates to pharmacologically potent and/or stable variants of human fibroblast growth factor 21 (FGF21), pharmaceutical compositions comprising FGF21 variants, and methods for treating type 2 diabetes, obesity, dyslipidemia, or metabolic syndrome, or any combination thereof, using such variants.

This present invention relates to variants of human fibroblast growthfactor 21 (FGF21), pharmaceutical compositions comprising FGF21variants, and methods for treating type 2 diabetes, obesity,dyslipidemia, or metabolic syndrome, or any combinations thereof.

FGF21 is a hormone that functions as an important metabolic regulator ofglucose and lipid homeostasis. FGF21 promotes glucose uptake inadipocytes by up-regulating GLUT1 expression, a mechanism distinct fromthat of insulin. In diabetic rodents and monkeys, human FGF21 loweredfasting serum concentrations of glucose, and reduced fasting serumconcentrations of triglycerides, insulin and glucagon. Furthermore, inrodent models of diet induced obesity, FGF21 administration led tocumulative body weight loss in a dose dependent manner. Thus, FGF21 haspotential utility for the treatment of diabetes, obesity, dyslipidemia,and metabolic syndrome.

Variants of human FGF21 have been described in WO2010/065439,WO2006/028595, and WO2005/061712.

Problems associated with human wild type FGF21 and known variants ofhuman FGF21 are the low pharmacological potency and/or pharmaceuticalstability of the molecules. Thus, there is still a need for alternativeFGF21 variants that are potent and/or stable.

The present invention provides alternative variants of human FGF21having advantages over human wild type FGF21 and known variants of humanFGF21 disclosed in the art. These advantages include improvedpharmacological potency and/or improved pharmaceutical stability.Certain FGF21 variants of the present invention have one or moreadvantageous physiochemical characteristics that are useful forefficient manufacturing and/or formulation as a therapeutic protein,including reduced proteolytic degradation in vivo, reducedsusceptibility to oxidation, lowered propensity to aggregate at highconcentrations, lowered levels of post-translational modificationsduring production in mammalian cell systems, increased compatibilitywith certain preservatives, and/or improved chemical stability.Additionally, the FGF21 variants of the present invention arepotentially useful for the treatment of type 2 diabetes, obesity,dyslipidemia, or metabolic syndrome or any combination thereof.

The present invention provides a variant of human fibroblast growthfactor 21 (FGF21), wherein the amino acid sequence is

(SEQ ID NO: 13) HPIPDSSPLLQFGGQVRQRYLYTDDAQQTECHLEIREDGTVGCAADQSPESLLQLKALKPGVIQILGVKTSRFLCQRPDGALYGSLHFDPEACSFR EX ₁LLEDGYNVYQSEAHGLX₂LHLPGDKSPHRKPAPRGPARFLPLPGLP PALPEPPGILAPQPPDVGSSDPX ₃ X ₄LVX₅PSQLLSPSFLGwherein X₁ is L or D, X₂ is P or W, X₃ is L or Y, X₄ is S or R, and X₅is G or E.

The present invention provides a variant of human fibroblast growthfactor 21 (FGF21), wherein the amino acid sequence is

(SEQ ID NO: 1) HPIPDSSPLLQFGGQVRQRYLYTDDAQQTECHLEIREDGTVGCAADQSPESLLQLKALKPGVIQILGVKTSRFLCQRPDGALYGSLHFDPEACSFREDLLEDGYNVYQSEAHGLPLHLPGDKSPHRKPAPRGPARFLPLPGLPPALPEPPGILAPQPPDVGSSDPLRLVEPSQLLSPSFLG.

The present invention also provides a pharmaceutical compositioncomprising a variant of human FGF21 of the present invention, asdescribed herein, and at least one pharmaceutically acceptable carrier,diluent, or excipient, and optionally other therapeutic ingredients.

The present invention also provides a method of treating type 2diabetes, obesity, dyslipidemia, or metabolic syndrome, or anycombination thereof, in a patient comprising administering to thepatient a variant of human FGF21 of the present invention, as describedherein.

The present invention also provides a method of treating type 2diabetes, obesity, dyslipidemia, or metabolic syndrome, or anycombination thereof, in a patient comprising administering to thepatient a pharmaceutical composition of the present invention, asdescribed herein.

Furthermore, the present invention provides a variant of human FGF21 ofthe present invention, as described herein, for use in therapy.Preferably, the present invention provides a variant of human FGF21 ofthe present invention, as described herein, for use in the treatment oftype 2 diabetes, obesity, dyslipidemia, or metabolic syndrome, or anycombination thereof.

Furthermore, the present invention provides the use of a variant ofhuman FGF21 of the present invention, as described herein, in themanufacture of a medicament for the treatment of type 2 diabetes,obesity, dyslipidemia, or metabolic syndrome, or any combinationthereof.

Full length human wild type FGF21 is a 208 amino acid polypeptidecontaining a 27 amino acid signal peptide. Mature human wild type FGF21comprises the full length polypeptide without the 27 amino acid signalpeptide, resulting in a 181 amino acid polypeptide (SEQ ID NO:2). Thechanges in amino acid positions of the FGF21 variants of the presentinvention are determined from the amino acid positions in thepolypeptide of mature human wild type FGF21 (SEQ ID NO:2). Thus, asubstitution described herein as “A31C” refers to substitution of theamino acid Cys for the wild type amino acid Ala at position 31 of themature human wild type FGF21 protein.

It is important to note that a substitution of one amino acid residue ina particular variant may affect the characteristics of the variants as awhole, and that overall effect may be beneficial or detrimental to thepharmacological potency and/or pharmaceutical stability. For example,one amino acid substitution, P115W, increases the potency of the FGF21variant, however P115W is also believed to contribute to theself-interactions that cause aggregation (see Example 5). Therefore, theoverall effect is detrimental to the variants, and thus the substitutionP115W is not included in the preferred FGF21 variants of the presentinvention.

Certain variants of human FGF21 of the present invention are potent,biologically active proteins as demonstrated for SEQ ID NO:1 in Examples2 and 3. The preferred FGF21 variants of the present invention containamino acid substitutions that together not only improve pharmacologicalpotency, but also are compatible with other amino acid changes that, inturn, provide for improved physiochemical properties and increased invivo stability. The group of amino acid substitutions in the preferredFGF21 variants of the present invention that improve potency includeD127K, S167R, G174L, R175L, and A180L (see Examples 2 and 3).

Exposure of a concentrated protein solution of human wild type FGF21 toa pharmaceutical preservative, such as m-cresol, increases thepropensity of the protein to form aggregates. Structural stabilizationthrough the introduction of an additional disulfide bond improves thepreservative compatibility as well as the thermal stability of humanwild type FGF21. The FGF21 variants of the present invention incorporatethe amino acid substitutions A31C and G43C that greatly improve thermalstability and preservative compatibility without compromising biologicalactivity. High potency variants of FGF21 that also include the A31C/G43Csubstitutions have been described previously. Those reported variantsdisplay significantly improved preservative compatibility relative towild type FGF21, but they are still prone to aggregation. Aggregation isknown to increase the risk of immunogenicity, thereby reducing theacceptability of the variants as a therapeutic protein.

To minimize this detrimental aggregation, preferred variants of thepresent invention include the amino acid substitution L98D, whichresults in a significantly lower high molecular weight aggregateformation at high concentrations (see Example 5). Advantageously, theamino acid substitution L98D does not decrease the potency of thevariants.

A preferred commercial expression system for manufacture of the FGF21variants of the present invention is the mammalian CHO-K1 cell line.However, the mammalian cell lines CHO-K1 and HEK293 may causepost-translational modifications to mature human wild type FGF21 throughsulfation of the tyrosine side chain at position 179. Sulfation oftyrosine residues at positions 179 and 180 (if present) decreasespotency and is an undesirable source of product heterogeneity. Thus,when an FGF21 protein having Tyr at position 179 and/or 180 is expressedfrom CHO-K1 or HEK293 cell lines, some proportion of the expressedproteins may be sulfated at position 179, others may be sulfated atposition 180, while others may be sulfated at both positions and some atneither position. This leads to a heterogeneous and unpredictableprotein population with decreased potency.

The FGF21 variants of the present invention resolved this detrimentalsulfation by including the amino acid substitution Y179F into thevariants. Y179F eliminates the sulfation resulting from production inCHO-K1 and HEK293 cells (see Example 4). Moreover, the amino acidsubstitution Y179F is compatible with the other favored amino acidsubstitutions of the present invention, and is determined to be aneutral change with regard to potency.

Human wild type FGF21 is susceptible to proteolytic degradation in vivo.A major proteolytic fragment recovered from sera after intravenous orsubcutaneous injection of mice or cynomolgus monkeys is the fragmentthat terminates at position 171. Previously, the FGF21 fragment spanningresidues 1 to 171 has been determined to be ˜100-fold less potent in invitro potency assays. Eliminating this proteolytic cleavage siteimproves drug efficacy by increasing exposure to active drug. The aminoacid substitution G170E has been shown to significantly slow cleavage inmouse (data not shown) and virtually eliminate proteolysis at the 171position after 24 hours in cynomolgus monkeys (see Example 6). The G170Esubstitution does not impact potency and is compatible with the desiredphysiochemical stability profile. Therefore, the amino acid substitutionG170E is incorporated into the preferred FGF21 variants of the presentinvention.

Human wild type FGF21 is susceptible to a carboxypeptidase produced inCHO-K1 manufacture, and the amino acid substitution S181G slows thisprocessing, thereby reducing heterogeneity of the length of the proteinexpressed (i.e., heterogeneity in the number of amino acid residues inthe mature protein expressed by the cell line). Although the amino acidsubstitution S181G does not eliminate C-terminal proteolysis inmammalian cell expression, it is quite effective at slowing proteolysiswhile maintaining the desired potency in the context of other desiredamino acid substitutions found in the FGF21 variants of the presentinvention. In view of this advantageous characteristic, the amino acidsubstitution S181G is incorporated into the FGF21 variants of thepresent invention.

The present invention also encompasses polynucleotides encoding theabove-described variants that may be in the form of RNA or in the formof DNA, which DNA includes cDNA and synthetic DNA. The DNA may bedouble-stranded or single-stranded. The coding sequences that encode thevariants of the present invention may vary as a result of the redundancyor degeneracy of the genetic code.

The polynucleotides that encode for the variants of the presentinvention may include the following: only the coding sequence for thevariants, the coding sequence for the variants and additional codingsequence such as a functional polypeptide, or a leader or secretorysequence or a pro-protein sequence; the coding sequence for the variantsand non-coding sequence, such as introns or non-coding sequence 5′and/or 3′ of the coding sequence for the variants. Thus the term“polynucleotide encoding a variant” encompasses a polynucleotide thatmay include not only coding sequence for the variants but also apolynucleotide which includes additional coding and/or non-codingsequence.

The polynucleotides of the present invention will be expressed in a hostcell after the sequences have been operably linked to an expressioncontrol sequence. The expression vectors are typically replicable in thehost organisms either as episomes or as an integral part of the hostchromosomal DNA. Commonly, expression vectors will contain selectionmarkers, e.g., tetracycline, neomycin, and dihydrofolate reductase, topermit selection of those cells transformed with the desired DNAsequences.

The FGF21 variants of the present invention may readily be produced inmammalian cells such as CHO, NS0, HEK293 or COS cells; in bacterialcells such as E. coli, Bacillus subtilis, or Pseudomonas fluorescence;or in fungal or yeast cells. The host cells are cultured usingtechniques well known in the art. The preferred mammalian host cell isthe CHOK1SV cell line containing a glutamine synthetase (GS) expressionsystem (see U.S. Pat. No. 5,122,464).

The vectors containing the polynucleotide sequences of interest (e.g.,the variants of FGF21 and expression control sequences) can betransferred into the host cell by well-known methods, which varydepending on the type of cellular host. For example, calcium chloridetransfection is commonly utilized for prokaryotic cells, whereas calciumphosphate treatment or electroporation may be used for other cellularhosts.

Various methods of protein purification may be employed and such methodsare known in the art and described, for example, in Deutscher, Methodsin Enzymology 182: 83-89 (1990) and Scopes, Protein Purification:Principles and Practice, 3rd Edition, Springer, NY (1994).

The pharmaceutical compositions of the FGF21 variants of the presentinvention may be administered by any means known in the art that achievethe generally intended purpose to treat type 2 diabetes, obesity,dyslipidemia, or metabolic syndrome, or any combination thereof. Thepreferred route of administration is parenteral. The dosage administeredwill be dependent upon the age, health, and weight of the recipient,kind of concurrent treatment, if any, frequency of treatment, and thenature of the effect desired. Typical dosage levels can be optimizedusing standard clinical techniques and will be dependent on the mode ofadministration and the condition of the patient and can be determined bya person having ordinary skill in the art.

The FGF21 variants of the present invention are formulated according toknown methods to prepare pharmaceutically useful compositions. A desiredformulation is a stable lyophilized product that is reconstituted withan appropriate diluent or an aqueous solution of high purity withoptional pharmaceutically acceptable carriers, preservatives, excipientsor stabilizers [Remington, The Science and Practice of Pharmacy, 19thedition, Gennaro, ed., Mack Publishing Co., Easton, Pa. 1995].

The FGF21 variants of the present invention may be combined with apharmaceutically acceptable buffer, and the pH adjusted to provideacceptable stability, and a pH acceptable for administration. Moreover,the FGF21 variants of the present invention may be placed into acontainer such as a vial, a cartridge, a pen delivery device, a syringe,intravenous administration tubing or an intravenous administration bag,wherein the container is a unit dose container.

The term “dyslipidemia” means a disorder of lipoprotein metabolism,including lipoprotein overproduction or deficiency. Dyslipidemia may bemanifested by elevation of the total cholesterol, low-densitylipoprotein (LDL) cholesterol and the triglyceride concentrations,and/or a decrease in high-density lipoprotein (HDL) cholesterolconcentration in the blood.

The term “metabolic syndrome” is characterized by a group of metabolicrisk factors in one person. They include: abdominal fat—in most men, a40-inch waist or greater; high blood sugar—at least 110 milligrams perdeciliter (mg/dl) after fasting; high triglycerides—at least 150 mg/dLin the bloodstream; low HDL—less than 40 mg/dl; and/or, blood pressureof 130/85 or higher.

The term “obesity” is defined as a condition in which there is an excessof subcutaneous fat in proportion to lean body mass (Stedman's MedicalDictionary 28th edition, 2006, Lippincott Williams & Wilkins).

A “patient” is a mammal, preferably a human.

The term “treating” (or “treat” or “treatment”) means slowing, reducing,or reversing the progression or severity of a symptom, disorder,condition, or disease.

The term “therapeutically effective amount” refers to the amount or doseof variants of FGF21 of this invention which, upon single or multipledose administration to a patient, provides the desired treatment.

The term “type 2 diabetes” is characterized by excess glucose productionin spite of the availability of insulin, and circulating glucose levelsremain excessively high as a result of inadequate glucose clearance.

The following examples may be performed essentially as described below.

EXAMPLE 1 Expression of FGF21 Variants in CHOK1SV Cells

The FGF21 variants of the present invention are produced in a mammaliancell expression system using Chinese hamster ovary (CHOK1SV) cells.Genes coding for FGF21 variants are subcloned into the glutaminesynthetase (GS)-containing expression plasmid backbones (pEE12.4-basedplasmids). The cDNA sequence encoding the FGF21 variants is fused inframe with the coding sequence of preferred signal peptide sequences toenhance secretion of the desired product into the tissue culture medium.The preferred signal peptide sequences are the polypeptides as shown inthe amino acid sequences SEQ ID NO:3, SEQ ID NO:4, SEQ ID NO:5, or SEQID NO:6.

The expression is driven by the viral cytomegalovirus (CMV) promoter.CHOK1SV cells are stably transfected using electroporation and theappropriate amount of recombinant expression plasmid, and thetransfected cells are maintained in suspension culture, at the adequatecell density. Selection of the transfected cells is accomplished bygrowth in methionine sulfoximine (MSX)-containing serum-free medium andincubated at 35-37° C. and 5-7% CO₂.

Clonally-derived cell lines are generated by use of a flow cytometer.The expression of an FGF21 variant in mammalian cells generally yieldsthe natural N-terminal sequence, HPIP, i.e. without a methionine residueat the N-terminus, such as the FGF21 variant shown by the amino acidsequence of SEQ ID NO:1.

FGF21 variants secreted into the media from the CHO cells are purifiedby a process by which the clarified cell culture medium is heated to50-60° C. for up to two hours, cooled, treated with detergent (TritonX-100) for viral inactivation, and is applied to a Capto MMC (GEHealthcare) mixed mode chromatography column. The FGF21 variant iseluted from the column using a pH 8 buffer, and the subsequent productpool is adjusted with 50 mM citric acid, 150 mM NaCl solution to a pHrange of 3.2 to 3.5 for one hour for viral inactivation. The solution isadjusted to between pH 6.7 to 7.3 by addition of Tris buffer and theFGF21 variant is further purified by hydrophobic exchange chromatographyusing Phenyl Sepharose High Performance resin (GE Healthcare). Thehydrophobic interaction column is eluted with a decreasing gradient ofsodium sulfate at pH 7. The HIC purified FGF21 variant is bufferexchanged into a Tris buffer at pH 8 containing NaCl and is furtherpurified by anion exchange chromatography on Source 30Q resin (GEHealthcare). The anion exchange column is eluted with an increasingconcentration of sodium chloride at pH 8. Purified FGF21 variant ispassed through a Planova 20N (Asahi Kasei Medical) viral retentionfilter followed by concentration/diafiltration into 10 mM citrate, 150mM NaCl pH 7 using tangential flow ultrafiltration on a regeneratedcellulose membrane (Millipore).

EXAMPLE 2 3T3-L1-βKlotho Fibroblast Glucose Uptake Assay

3T3-L1-βKlotho fibroblasts are generated from 3T3-L1 fibroblasts byretroviral transduction of a CMV-driven mammalian expression vectorcontaining the coding sequence of wild type mouse βKlotho and ablasticidin resistance marker. Blasticidin-resistant cells are selectedafter growth for 14 days in the presence of 15 μM blasticidin, andβKlotho protein expression is verified by immunoblot with ananti-βKlotho antibody. The 3T3-L1-βKlotho fibroblasts are maintained inDulbecco's Modified Eagle Medium (DMEM) with 10% calf serum, and 15 μMblasticidin until plated for experimental use.

For glucose uptake, 3T3-L1-βKlotho fibroblasts are plated at 20,000cells/well in 96-well plates and incubated for 48 hours in DMEM with 10%calf serum. The cells are incubated for 3 hours in DMEM with 0.1% bovineserum albumin (BSA) with or without an FGF21 variant of interest,followed by 1 hour incubation in Krebs—Ringer phosphate (KRP) buffer (15mM Hepes, pH 7.4, 118 mM NaCl, 4.8 mM KCl, 1.2 mM MgSO₄, 1.3 mM CaCl₂,1.2 mM KH₂PO₄, 0.1% BSA) containing 100 μM 2-deoxy-D-(¹⁴C) glucose withor without an FGF21 variant. Non-specific binding is determined byincubation of select wells in Krebs—Ringer bicarbonate/Hepes (KRBH)buffer containing 1 mM 2-deoxy-D-(¹⁴C) glucose. The reaction isterminated by addition of 20 μM cytochalasin B to the cells and glucoseuptake is measured using a liquid scintillation counter.

The in vitro potency of the FGF21 variant of SEQ ID NO:1 in the3T3-L1-βKlotho fibroblast glucose uptake assay was 0.026 nM. The FGF21variant of SEQ ID NO:1 is a potent FGF21 variant when compared to theknown FGF21 variant of SEQ ID NO:11 (disclosed in WO 2006/028595). Thein vitro potency of the FGF21 variant of SEQ ID NO:11 in the3T3-L1-βKlotho fibroblast glucose uptake assay was 0.49 nM.

EXAMPLE 3 Human 293 Cell-βKlotho-SRE luciferase Assay

Construction of 293-βKlotho-SRE luc Reporter Cells:

HEK-293 (human embryonic kidney cells) are cultured at 37° C., 5% CO₂ ingrowth medium containing 10% fetal bovine serum (FBS) in Dulbecco'smodified Eagle's medium. Cells are cotransfected with a plasmidcontaining a CMV promoter driven human βKlotho expression cassette and aplasmid containing a Serum Response Element (SRE) driven luciferaseexpression cassette. The βKlotho expression plasmid also contains anSV40 promoter driven neomycin phosphotransferase expression cassette toconfer resistance to the aminoglycoside antibiotic G418. TransfectedHEK-293 cells are selected with 600 μg/mL of G418 to select for cellswhere the transfected plasmids have been integrated into the genome.Selected cells are cloned by dilution and tested for an increase inluciferase production at 24 hours post addition of FGF21. The clonedemonstrating the largest FGF21 dependant increase in luciferase ischosen as the cell line used to measure relative FGF21 variantsactivity.

293-βKlotho-SRE luc FGF21 Activity Assay:

293-βKlotho-SRE luc cells are rinsed and placed into CD 293 suspensionculture media (Invitrogen). Cells are grown in suspension overnight at37° C., 6% CO₂, 125 rpm. Cells are counted, pelleted by centrifugation,and re-suspended in CD 293 media containing 0.1% BSA. Cells are placedin white 96 well plates at 25,000 cells per well. A four-fold serialdilution in CD 293/0.1% BSA is prepared for each FGF21 variant togenerate eight dilutions with final concentrations from 100 nM to 0.006nM. Dilutions are added to cells in triplicate and incubated for 16-20hours at 37° C., 5% CO₂. Luciferase level is determined by the additionof an equal volume of OneGlo™ luciferase substrate (Promega) andmeasuring relative luminescence. Data is analyzed using a four parameterlogistic model (XLfit version 5.1) to fit the curves and determine EC₅₀.

The in vitro potency of the FGF21 variant of SEQ ID NO:1 in the human293 cell-βKlotho-SRE luc assay was 0.25 nM. The FGF21 variant of SEQ IDNO:1 is a potent FGF21 variant when compared to the known FGF21 variantof SEQ ID NO:11 (disclosed in WO 2006/028595). The in vitro potency ofthe FGF21 variant of SEQ ID NO:11 in the human 293 cell-βKlotho-SRE lucassay was 22.39 nM.

EXAMPLE 4 Tyrosine Sulfation During Manufacturing in Mammalian Cells

Human wild type FGF21 is susceptible to tyrosine sulfation at position179 during mammalian protein expression in CHOK1SV cells (data notshown). This sulfation leads to product heterogeneity, meaning thatdifferent forms of the protein (i.e., with and without sulfation) mayoccur. Product homogeneity is a desired attribute of a biopharmaceuticalproduct. Post-translational modifications that occur during productionof a therapeutic protein are undesirable as the modifications can leadto differences in activity or other biopharmaceutical properties.

To assess whether an FGF21 variant is sulfated, a 1 μL aliquot of thesample is mixed with 99 μL of 0.1% trifluoroacetic acid (TFA). Thesample is analyzed by liquid chromatography—mass spectrometry (LC-MS),using the following conditions: the mobile phase A is 0.1% TFA/10%acetonitrile, the mobile phase B is 0.1% TFA in acetonitrile, the columnis a C8 column, 3.5 μm 2.1×150 mm, with 2.1×12.5 mm C8 guard, theinjection volume is 12-20 μL depending on sample concentration so thatapproximately 1 μg of protein is injected.

TABLE 1 Gradient Conditions for Liquid Chromatographic Separation Time(min) 0 12 15 15.1 20 21.1 30 % B 10 50 60 90 90 10 10 Flow (μL/min) 200200 200 200 200 200 200A Waters Micromass LCT Premier™ mass spectrometer is set up to a massrange between 400 to 1990 amu, polarity ES+, capillary 2000, sample cone40 V, aperture 1 is 30 V, the source temperature is 105° C., cone gasflow is 50 L/hour, desolvation temperature is 300° C., and thedesolvation gas flow is 600 L/hour.

TABLE 2 LC/MS Characterization of FGF21 variant of SEQ ID NO: 1 ProductExpected Mass Observed Mass % Error Rel % 1-181 19633.3 19633.0 0.00233.8 1-180 19576.2 19576.1 0.001 66.2

As can be seen from Table 2, the expected mass (having no sulfation) wasapproximately the same as the observed mass for the FGF21 variant of SEQID NO:1, indicating that sulfation was not detected in the FGF21 variantof SEQ ID NO:1. Thus, the amino acid substitution Y179F preventedsulfation from occurring at position 179 in the FGF21 variant of SEQ IDNO:1. This result provides a more homogeneous product, making it moreacceptable as a therapeutic protein product.

EXAMPLE 5 P115W Promotes Aggregation, Whereas L98D Increases PhysicalStability and Compatibility with Benzyl Alcohol in the Formulation

To measure the amount of protein self-association and aggregation, ananalytical size exclusion chromatography (SEC) method is used to measurethe percent of high molecular weight (% HMW) aggregates. Initial stocksolutions of protein are characterized by SEC to determine the startinglevels of HMW (Table 3).

TABLE 3 FGF21 variants Starting Level of HMW (%) FGF21 variant of SEQ IDNO: 10 3.2 FGF21 variant of SEQ ID NO: 1 0.21 FGF21 variant of SEQ IDNO: 8 3.6 FGF21 variant of SEQ ID NO: 9 0.12

Samples of each protein are prepared by dialyzing (using dialysiscassettes with molecular weight cutoff of 10,000 daltons) into samplebuffers (described in Tables 4-6) at a concentration of 2 mg/mLovernight at 4° C. After dialysis, samples are sterile filtered (0.22 μmmembrane) and quantified by absorbance at 280 nm. Next, samples areconcentrated to a target concentration of ≧60 mg/mL at 3000 rpm at 4° C.using 10,000 MW cut-off centrifuge filters. After concentrating samples,the protein concentration is quantified by absorbance at 280 nm, and the% HMW is determined using an SEC assay.

The SEC method utilizes a TosoHaas model TSK-GEL® G2000SW_(XL) columnwith dimensions 30 cm×0.78 cm. Mobile phase is 0.1 M sodium phosphate,pH 7.4 at a flow rate of 0.5 mL/minute. Low concentration samples areapplied as 10 μL injections and monitored at an absorbance wavelength of214 nm, whereas concentrated samples are applied as 1 μL injections andmonitored at 280 nm.

Table 4 reports protein concentration and % HMW in the concentratedsolutions of the FGF21 variants SEQ ID NO:8 and SEQ ID NO:9. Thepercentage of each variant remaining in the monomeric (non-aggregatedfrom) is not listed in the table but is equal to 100% minus the reported% HMW. The FGF21 variant of SEQ ID NO:8 and the FGF21 variant of SEQ IDNO:9 differ only at amino acid position 115 with the FGF21 variant ofSEQ ID NO:8 containing a potency enhancing residue tryptophan at 115(P115W) and the FGF21 variant of SEQ ID NO:9 containing the wild typeresidue proline (P115P). Under various formulation buffer conditions,the % HMW for the FGF21 variant of SEQ ID NO:8 (P115W) was significantlyhigher compared to the FGF21 variant of SEQ ID NO:9, demonstrating thecausal effect of having tryptophan at position 115 on promotingaggregation and self-association. Likewise, the FGF21 variant of SEQ IDNO:10, which contains the tryptophan residue at position 115, hassubstantially elevated % HMW compared to the FGF21 variant of SEQ IDNO:1, which contains the amino acid proline at position 115 (Table 5).

TABLE 4 Propensity for Aggregation as Measured by SEC FGF21 variantFGF21 variant of SEQ of SEQ ID NO: 8 (P115W) ID NO: 9 (P115P) Conc.Conc. Buffer Composition (mg/mL) % HMW (mg/mL) % HMW Phosphate buffersaline 65 32.3 67 0.38 pH7.4 10 mM Histidine pH7.0, 62 34.3 63 0.47 150mM NaCl 10 mM Tris pH 8.0, 65 26.5 64 0.34 150 mM NaCl 10 mM HistidinepH 7.0, 72 29.2 81 0.42 150 mM NaCl, 0.2M L-arginine 10 mM Histidine pH7.0, 70 49.6 50 3.5 50 mM NaCl

TABLE 5 Propensity for Aggregation as Measured by SEC FGF21 variantFGF21 variant of SEQ of SEQ ID NO: 10 (P115W) ID NO: 1 (P115P) Conc.Conc. Buffer Composition (mg/mL) % HMW (mg/mL) % HMW Phosphate buffersaline 77 33.7 88 0.56 pH7.4 10 mM Histidine pH7.0, 83 37.5 61 0.69 150mM NaCl 10 mM Tris pH8.0, 63 25.1 71 2.4 150 mM NaCl 10 mM HistidinepH7.0, 64 27.8 85 2.6 150 mM NaCl, 0.2M L- arginine 10 mM HistidinepH7.0, 58 45.9 61 8.2 50 mM NaCl

Physical stability and compatibility with benzyl alcohol at apreservative-level concentration of 0.9% is measured as % HMW in the SECassay, monitored in the buffer 10 mM histidine at pH 7.0 with 150 mMNaCl, in the presence or absence of 0.02% Tween-80. Samples are preparedat 30 mg/mL and incubated at 4° C., 25° C., and 40° C. for 4 weeks.Freshly formulated FGF21 variants (i.e., at time zero) and thoseincubated for 4 weeks are analyzed for % HMW by the SEC method. Table 6summarizes results of the analyses, comparing time zero samples(“Initial”) and those incubated 4 weeks at 40° C.

TABLE 6 Propensity for Aggregation and Preservative Compatibility at 30mg/mL Formulation Concentration FGF21 variant FGF21 variant of SEQ ofSEQ ID NO: 9 (L98L) ID NO: 1 (L98D) 4 weeks at 4 weeks at Initial 40° C.Initial 40° C. Buffer Composition (% HMW) (% HMW) (% HMW) (% HMW) 10 mMHistidine, pH7.0, 0.97 18.3 6.0 5.6 150 mM NaCl 10 mM Histidine, pH7.0,11.0 33.9 4.2 6.0 150 mM NaCl, 0.9% benzyl alcohol 10 mM Histidine,pH7.0, 11.0 32.1 4.3 5.3 150 mM NaCl, 0.9% benzyl alcohol, 0.02%Tween-80

The FGF21 variant of SEQ ID NO:1 contains the amino acid substitutionL98D. The FGF21 variant of SEQ ID NO:9 does not contain the amino acidsubstitution L98D and instead contains the wild type amino acid leucineat position 98. The benefit of the amino acid substitution L98D isobserved when each protein is formulated at 30 mg/mL under formulationconditions (Table 6). Under all conditions tested, stressing the FGF21variants for 4 weeks at 40° C. results in a substantially higher % HMWfor the FGF21 variant of SEQ ID NO:9 compared to the FGF21 variant ofSEQ ID NO:1. Furthermore, addition of 0.9% benzyl alcohol, a commonpreservative used in a multi-use pharmaceutical preparation, exacerbatesthe increase in % HMW for the FGF21 variant of SEQ ID NO:9 but not forthe FGF21 variant of SEQ ID NO:1. This incompatibility with benzylalcohol is also observed in the analysis of the initial samplepreparation, where the % HMW in the presence of 0.9% benzyl alcohol is11%, compared to only 0.97% in the absence of benzyl alcohol. Neitherthe FGF21 variant of SEQ ID NO:9 nor the FGF21 variant of SEQ ID NO:1contain the P115W residue, thus, the poor physical stability under theseconditions cannot be attributed to the P115W residue. After the aminoacid substitution L98D is made, enhanced physical stability in thepresence of 0.9% benzyl alcohol is observed.

These data indicate that certain substitutions can affect the stabilityof overall protein due to aggregation into high molecular weightspecies, particularly in the presence of certain preservatives such asbenzyl alcohol. Minimization of these HMW aggregates is preferred fortherapeutic proteins. This can be accomplished through certainsubstitutions in the FGF21 variants protein, such as L98D in the FGF21variants shown in SEQ ID NO:1. Other substitutions, such as P115W, canhave detrimental effects, such as increasing the level of aggregation inthe variants.

EXAMPLE 6 Proteolytic Degradation In Vivo

Male cynomolgus monkeys, n=2/group are dosed subcutaneously with asingle 2 mg/kg injection of the FGF21 variant of SEQ ID NO:1. Serum isobtained over the time course (withdrawn after 0.25 to 12 hours) for 24hour evaluation of in vivo proteolysis via mass spectrometry to quantifythe amount of active compound.

Liquid chromatographic mass spectrometry (LC/MS) analysis is performed.A 100 μL aliquot of each serum sample is immunoprecipitated withanti-FGF21 monoclonal antibodies which are covalently bound to magneticbeads. The immunoprecipitated samples are split into separate aliquots,allowing detection of intact proteins and tryptically-digested proteins.Intact proteins are injected onto a Discovery® Bio wide pore column,100×0.32 mm i.d. containing 3 μm particles coated with C5.Tryptically-digested samples are injected onto a Discovery Biowide Porecolumn, 100×0.32 mm i.d. containing 3 μm particles coated with C18.Chromatographic conditions for all injections use binary gradientsconsisting of mobile phase A (0.1/100, formic acid:water) and mobilephase B (0.1/100, formic acid:acetonitrile). The effluent from the LC isdirectly connected to a Micromass Synapt® Q-Tof mass spectrometer formass spectral detection in positive ion mode. Data from the Q-Tof massspectrometer are collected using Masslynx (v 4.1) and MaxEnt1deconvolution software.

Cleavage at position 171 of FGF21 proteins has been found to reducebioactivity of the protein by over 100-fold. Thus, reducing theproteolysis at this site is desirable to enhance exposure offully-active drug. The FGF21 variant of SEQ ID NO:1, when analyzed in anLC/MS method as above, shows no detectable proteolysis products over the24 hour evaluation. These data demonstrate the substitution of G170E inthe FGF21 variant of SEQ ID NO:1 diminishes in vivo proteolyticdegradation over 24 hours in male cynomolgus monkeys when compared tothe FGF21 variant of SEQ ID NO:7, which does not contain the amino acidsubstitution of G170E.

EXAMPLE 7 Glucose Lowering in Ob/Ob Mouse Model

Male ob/ob (B6.V-Lep^(ob)/Lep⁺/OlaHsd) mice and age-matched ob/m leancontrols (B6.V-Lep⁺/OlaHsd) are 7-8 weeks of age upon arrival and 10-11weeks of age at initiation of treatment. Upon arrival, all mice arehoused 3 per cage and allowed to acclimate for 3 weeks before the startof treatment. The mice are fed Purina Rodent Chow 5015 and given waterad libitum. The mice are housed in 12-hour light/dark cycle with ambienttemperature set at 70° F. The day prior to initiation of treatment, themice are fasted for 2 hours and blood samples are collected via tailbleed into heparinized capillary tubes. Blood glucose levels aremeasured with an Ascensia Contour blood glucose meter and plasma insulinlevels are quantified using the Meso Scale mouse/rat insulin assay kit(Meso Scale Discovery, Gaithersburg, Md.). On the day of treatmentinitiation (day 0), the mice are sorted based on previous day's bodyweight, blood glucose, and plasma insulin. The FGF21 variants arediluted with sterile saline (0.9% NaCl) and administered subcutaneouslyvia mini-osmotic Alzet pumps. On day 5, fed blood glucose and plasmainsulin levels are measured approximately 2 hours after the start of thelight cycle. All mice are fasted overnight on day 5 and an oral glucosetolerance test (OGTT) is performed on day 6. The mice are bled via tailsnip into heparinized capillary tubes prior to oral administration ofglucose (2 g/kg). Additional blood samples are collected 30, 60, and 120minutes after oral glucose administration. Plasma glucose is measuredwith a glucose assay kit from Cayman Chemicals. A four parameterlogistic regression model fit is performed on the normalized glucose AUCvalues on day 6.

On day 5, vehicle-treated mice were hyperglycemic with mean bloodglucose levels measured at 240.4±15.0 mg/dl (mean±SEM), while ob/m leancontrol mice had blood glucose levels of 150.6±6.0 mg/dl (mean±SEM).Both the FGF21 variant of SEQ ID NO:1 and the FGF21 variant of SEQ IDNO:11 lowered blood glucose in a dose-dependent manner to levelscomparable to the ob/m lean controls. The ED₅₀ of the FGF21 variant ofSEQ ID NO:1 was 0.7 μg/kg/hr, while the ED₅₀ of the FGF21 variant of SEQID NO:11 was 3.1 μg/kg/hr. The FGF21 variant of SEQ ID NO:1 wasapproximately 4.4-fold more potent at lowering blood glucose in ob/obmice than the FGF21 variant of SEQ ID NO:11. Therefore, the FGF21variant of SEQ ID NO:1 is a potent FGF21 variant when compared to theknown FGF21 variant of SEQ ID NO:11 (disclosed in WO 2006/028595).

We claim:
 1. A variant of human fibroblast growth factor 21 (FGF21),wherein the amino acid sequence is (SEQ ID NO: 13)HPIPDSSPLLQFGGQVRQRYLYTDDAQQTECHLEIREDGTVGCAADQSPESLLQLKALKPGVIQILGVKTSRFLCQRPDGALYGSLHFDPEACSFR EX ₁LLEDGYNVYQSEAHGLX₂LHLPGDKSPHRKPAPRGPARFLPLPGLP PALPEPPGILAPQPPDVGSSDPX ₃ X ₄LVX₅PSQLLSPSFLG

wherein X₁ is L or D, X₂ is P or W, X₃ is L or Y, X₄ is S or R, and X₅is G or E.
 2. The variant of claim 1, wherein X1 is D, X2 is P, and X5is E.
 3. A method for treating type 2 diabetes, obesity, dyslipidemia,or metabolic syndrome, or any combination thereof, comprisingadministering the variant of claim 1 to a patient in need thereof.
 4. Amethod for treating type 2 diabetes, obesity, dyslipidemia, or metabolicsyndrome, or any combination thereof, comprising administering thevariant of claim 2 to a patient in need thereof.
 5. A pharmaceuticalcomposition comprising the variant of claim 1, and at least onepharmaceutically acceptable carrier, diluent, or excipient.
 6. Apharmaceutical composition comprising the variant of claim 2, and atleast one pharmaceutically acceptable carrier, diluent, or excipient.